In automated fabrication plants or inside a complex wafer-processing tool, work pieces travel from one process station to another. At these process stations various operations are performed on the work pieces. During processing certain events may occur that will require the system to shutdown or at the very least temporarily pause processing. These may include problems in a process station detected by examining the output of the process station or by detection of out of specification parameters in a system, among other problems. When this occurs, it is necessary to halt the processing of wafers in the system to prevent further damage. However, when the processing is halted, wafers of which the processing is halted may still be present in the system. These wafers block the continuation of further processing in the system after the alarm condition has been resolved. After resolving of the alarm condition that resulted in interruption of the process, the further processing or handling of these wafers of which the processing was interrupted needs to be defined before the system can be used for continued processing. Therefore, there is a need for a way to monitor for and handle conditions that require the interruption of processing in a process tool and, after interruption, the recovery of the system and continuation of further processing.
Part of this problem is addressed in U.S. Pat. No. 6,162,010 issued to Ishizawa et al. and entitled “Method of Recovering Object to be Treated After Interruption”. This patent discusses the recovery of a semiconductor wafer after a treatment is unexpectedly stopped for a reason such a loss of power to the processing machinery. This patent discloses recovering wafers to an original cassette if the wafers are cooled and allowing the wafers to cool if the wafers were in a reactor-processing chamber. This method suffers from several drawbacks. First, it is drawn to a single wafer processing system and is not easily adaptable to batch processing. Second the recovery method is rigid and does not allow for override by operator or temporary suspension.
International Publication WO 01/18623 A1 entitled “Real-Time Fault Detection” discloses a method for detecting faults in semiconductor wafers in a real time environment. In this disclosure, a method and system for determining if there are faults within a system is disclosed. If a fault in the manufacturing system exists, that information is sent to an interface that could shut down the process or provide information to an operator. Drawbacks to this invention include its lack of ability to override a fault detection or to handle a fault detection in a variety of ways.
Another approach is disclosed in U.S. Pat. No. 5,897,710 issued to Sato et al. entitled “Substrate Processing Apparatus and Substrate Processing Method”. In the invention of Sato et al, an inspection station is included with a processing system. The inspection station is able to inspect the wafers. When wafers fail inspection, further processing can be interrupted immediately.
A disadvantage of the methods described above is that the action of immediate interruption of a process might in itself create damage because the work pieces concerned receive only a partial treatment. It is questionable if completion of the treatment in a later stage will result in the desired end effect, without complications and negative side effects.
It is the objective of the present invention to provide in a system an method to deal with an alarm condition in a way that prevents the necessity of immediate process interruption and its disadvantages and to provide in pre-programmed, operator selectable recovery procedures after interruption has taken place.